Consumer prices have risen 2.1 percent in the past 12 months, the Labor Department said Tuesday. If maintained over time, that rate would exceed the Fed's target for inflation of 2 percent and signal a potential need to raise short-term interest rates from near zero.

Higher rates could possibly limit economic growth. But at a news conference, Yellen is suggesting that rising inflation may prove temporary. "The data that we're seeing is noisy," she says.

Fed officials closely monitor a separate inflation measure. That index amounted to 1.6 percent in April. Fed officials project that inflation will stay at or below the 2 percent target through 2016.